Process of preparing pyritiferous zinc-blende for magnetic separation.



UNTTED STATES PATENT @FFTCE.

GILBERT RIGG, 0F PALMERTON,

PENNSYLVANIA, ASSIGNOR TO NEW JERSEY ZINC COMPANY, OF NEW YORK, N. Y., ACORPORATION OF NEW JERSEY.

ioness,

N 0 Drawing. I

Specification of Letters Patent.

Application filed March 27, 1911.

Patented uly Mt, rare. Serial No. 617,211.

To all whom it may concern Be it known that I, GILBERT RIGG, a subjectof the King of Great Britain, residing at Palmerton, county of Carbon,State of Pennsylvania, have invented certain new and useful Improvementsin Processes of Preparing Pyritiferous Zinc-Blende for MagneticSeparation; and I do hereby declare the following to be a full, clear,and exact description of the invention, such as will enable othersskilled in the art to which it appertains to make and use the same.

This invention relates to a process for separating pyrite from zincblende and other minerals with which it is associated, by firstconverting the pyrite into pyrrhotite or magnetic sulfid, with thesimultaneous recovery of the sulfur in elementary form, and thereuponwithdrawing the pyrrhotite from the zinc blende or other non-magneticmaterial by means of magnetic attraction.

In the usual method of converting pyrite F e8 into pyrrhotite, the oreis partially roasted in a current of air, and the endeavor is made tointerrupt the roasting at a point when suliicient sulfur has been drivenoff to effect the desired conversion into pyrrhotite, whose formulavaries somewhat but is usually given as from Fe,S to Fe s If theroasting is not continued long enough, a certainamount of non-magneticpyrite is left unchanged, and if carried too far, nonmagnetic ferricoxid is produced, which is equally undesirable from the standpoint ofeffecting its subsequent separation. Moreover, there is a furtherobjection to converting thepyrite of the ore into pyrrhotite bypartially roasting in a current of air, in that the sulfur is driven offas SO mixed with large volumes of fire gases, so that the gas mixture istoo dilute and too impure to be available for sulfuric acid manufacture.The gas mixture is, therefore, usually delivered into the air, and notonly is the sulfur Wasted, but the gases thus discharged are veryinjurious to vegetation and cause much trouble.

By the practice of my invention, as hereinafter described, it isimpossible to pass beyond the point of converting the pyrite intopyrrhotite or magnetic sulfid, and the sulfur is. recovered in the formof elementary sulfur or brimstone, all loss and nuisance beingpractically obviated.

In carrying the process into effect, I heat the pyritiferous ore inamufile, or in a shaft, from which the fire gases and air are excluded.At temperatures ranging from 600 C. to 800 C. the pyrite gives up partof its sulfur, which passes over as sulfur vapor, and, leaving themuflie or shaft by suitable exit openings, is recovered in the form ofelementary sulfur in a suitable condenser. The pyrite by this treatment,is converted into pyrrhotite or magnetic sulfid and may thereupon beseparated from the zinc blende or other non-magnetic minerals with whichit is associated, by means of a magnetic separator. As hereinbeforenoted, it is a char acteristic feature of this method of treatment thatit is impossible to pass beyond the point of converting the pyrite intopyrrhotite or magnetic sulfid. After it has been so converted, furtherheating has no effect upon it, unless the temperature is carried to sucha degree as to fuse the charge, and this is easily avoided.Consequently, the heating'can be continued long enough to insure thecomplete conversion of the pyrite into pyrrhotite Without incurring anydanger from over-roasting. his insures the ultimate withdrawal by themagnetic separator from the zinc blende or other non-magneticconstituent of the ore of practically all of the pyrite originallycontained therein, with the incidental recovery of the elementary sulfuras a valuable by-product and the avoidance of injury to vegetationwhichwould be involved in discharging the sulfurin the form of SO intothe atmosphere.

Having thus described my invention, what I claim is:

1. The process of treating zinc blende associated with pyrite, so as torender said constituents capable of magnetic separation, which consistsin expelling a portion of the sulfur of the ,pyrite by heating thepyritiferous ore at a temperature below the fusing point of the pyriteand below the dissociation point of the zinc blende, thereby convertingthe pyrite constituent of the ore into a magnetic condition aspyrrhotite, and without altering the zinc blende constituent;substantially as described.

2. The process of treating zinc blende associated with pyrite, so as torender said constituents capable of magnetic separation,

which consists in heating the pyritiferous carry the pyrite beyond themagnetic con- 10 ore, with the exclusion of air, thereby exdition;substantially as described.

pelling a portion of the sulfur of the pyrite In testimon whereof Iaflix my signature, constituent of 318 ore and collliverting ithinto inpresence of two witnesses.

a magnetic con ition as pyrr otite, the eating operation being conductedat atempera- GILBERT RIGG' ture below the fusing point of the pyrite,Witnesses: whereby said conditions of the operation HENRY HARDENBERGH,insure against such desulfurization as would E. G. TAOY.

